The present invention relates to an electric cell module, more specifically to an electric cell module which is U-shaped as a whole to enable terminal connecting operations in one direction, which is highly rigid as a module to hardly undergo damage when subjected to external forces including vibration and also has a high natural frequency to undergo no damage under resonance with external vibrations, and which is suitably used as a power source for driving, for example, an electric vehicle.
There have recently been discussed use of nickel hydride rechargeable batteries as power sources for driving various kinds of machine tools, electric motor-assisted bicycles and electric vehicles. In such cases, for example, in an electric vehicle, an output voltage of 100 to 300 V is necessary.
In order to obtain such output voltage, a plurality of electric cells are usually connected in series to assemble an electric cell module, and after a plurality of such electric cell modules are connected in series, the resulting assembly of cell modules is supported by a supporting plate or the like and is as such contained in a container to assume an electric cell pack structure having a desired output voltage.
An example of the electric cell module is shown in FIG. 1. In this electric cell module A, five electric cells 1 are connected in series to assume a rod-shape as a whole. Here, if the rod-shaped module is covered entirely with a heat-shrinkage tube, it not only attains the primary objective of insulation but also can enhance the strength of the entire module. Cell connector portions 2 for connecting electric cells 1 generally have a structure described below.
The structure will be described based on FIG. 2 showing an exploded cross-sectional view.
First, there are prepared a dish-like connecting piece 2A that is made of a conductive material and has a stepped structure having a large-diameter portion and a small diameter portion, and also a ring-shaped intervenient piece 2B made of an insulating material. The upper opening in the large-diameter portion of the connecting piece 2A is of such a diameter as can permit insertion of a can bottom 1b of an electric cell to be connected thereby, whereas a through hole 2a permitting insertion of a positive terminal 1a of another electric cell to be connected is defined in the small-diameter portion.
Meanwhile, a through hole 2b permitting insertion of the small-diameter portion of the connecting piece 2A is formed in the intervenient piece 2B.
When electric cells 1 are connected to each other, the intervenient piece 2B is placed on the upper face of the lower electric cell 1, and then the connecting piece 2A is placed thereon. The intervenient piece 2B is located on an upper rim 1c of the lower electric cell 1, and the positive terminal 1a of that cell 1 penetrates through the through holes 2b and 2a to protrude into the small-diameter portion of the connecting piece 2A, and simultaneously the bottom face of the small-diameter portion is brought into contact with a positive plate 1d on which the positive electrode of the electric cell is formed.
Here, the small-diameter portion is designed to have a depth such that the bottom face thereof is brought into contact with the positive plate 1d, when these elements are arranged as described above.
Next, the small-diameter portion of the connecting piece 2A and the positive plate 1d of the electric cell on which the positive terminal is formed are subjected to resistance welding to fix the connecting piece 2A onto the top of the electric cell 1 and simultaneously to secure electrical connection therebetween.
Subsequently, a can bottom 1b of another electric cell 1 is put into the large-diameter portion of the connecting piece 2A to carry out, as such, resistance welding between the side face of the large-diameter portion of the connecting piece 2A and the can bottom 1b of the upper electric cell 1 to immobilize the upper cell 1 in the large-diameter portion of the connecting piece 2A and also to secure electrical connection between them.
Thus, two electric cells 1 are connected to each other mechanically and electrically through the connecting piece 2A. Here, the intervenient piece 2B is incorporated so as to prevent the short-circuiting phenomenon to be caused, for example, when the upper electric cell is tilted and as such brought into contact with the lower electric cell by a force like bending is applied to the entire electric cell module.
However, the conventional electric cell module A shown in FIG. 1 involves the following problems:
(1) Since the module as a whole assumes an I-shaped rod body and the cell connector portion 2 and each electric cell are connected to each other by resistance welding to form a point-connection structure, the module does not have very high strength and yields to external forces, particularly to flexural forces.
Therefore, for example, when a pack structure is to be assembled by containing the electric cell module A in a container such as of a synthetic resin, deliberate operations are required so that the modules are not bent. Meanwhile, troubles can happen that the electric cell module A is broken, if some external force is applied to the assembled pack structure.
(2) In this electric cell module A, the rod body composed essentially of electric cells connected in series has a positive terminal and a negative terminal at its ends respectively. Thus, when the rod body is contained in a container to assemble a pack structure, these terminals are to be connected to other parts in two directions. Further, when one operator performs this connecting operations, he or she must move from one position to another; whereas when two operators perform this operation, productivity in module assembly will be lowered.
(3) In addition, when the pack structure having the electric cell module A contained in a container is used as a drive power source of an electric vehicle and the like, the structure resonates with vibration of the vehicle itself or with external vibrations, due to the low natural frequency of the electric cell module A, to induce great vibrations, causing occasionally damage of the electric cell module A and other troubles.
While various kinds of automotive parts, taken for example, are subjected to tests according to the vibration testing methods for automobile parts of the Japanese Industrial Standards (JIS D1601) in the preset frequency range of 5 to 100 Hz. In order to solve the problems described above and in view of this circumstance, it is essential for electric cell modules to have a natural frequency of higher than 100 Hz so as to avoid the above frequency range.
It is an object of the present invention to provide an electric cell module of a novel structure, which has overcome the problems inherent in the conventional electric cell module A and which is, as a whole, highly rigid, enables terminal connecting operations in one direction and has a high natural frequency to be free from damage by resonance with vibrations applied thereto.
In order to attain the intended objective as described above, the present invention provides an electric cell module containing a pair of rod bodies arranged parallel to each other to be oriented in opposite polarities, each rod body containing a plurality of electric cells connected in series through cell connector portions; an electrical connecting structure formed on one end face of each rod body, the structure connecting the rod bodies electrically to each other; and a jig for coupling the rod bodies, the jig surrounding at least one juxtaposed pair of cell connector portions present at the same longitudinal position in the rod bodies.